Tight Spaces? Consider Alternative-Material Poles

Like most utilities, the Los Angeles Department of Water and Power (LADWP; Los Angeles, California) has used wood poles since the municipal utility was established more than 100 years ago. But in the last few years, as the industry has evolved toward using alternate material — such as recycled steel, reinforced concrete and fiberglass reinforced composite — so too has LADWP. A case can be made for other pole materials depending on the specific application.

Wood poles continue to be the preferred solution for normal distribution line extensions and the replacement of poles in easily accessible locations. But where there is limited access for guy stub poles or in rear property-line installations, and where a more rigid pole is required, LADWP sometimes uses alternative-material pole solutions.

Last year, three challenging pole installations caused LADWP to investigate the alternatives. These replacement projects included:

Replacing a wood pole between two buildings with a taller pole to accommodate primary wires

Replacing a partially washed-away and rotted wood pole on a steep incline

Replacing a wood pole in the backyard of a residence that was on a hillside near a creek.

Replacing the existing poles with wood poles did not appear possible because of the space and other site limitations. Adding to their respective challenges, all three installations needed to be done cost-effectively and with minimal disruption to service. LADWP's Development and Standards Group determined that alternative-material poles were an obvious consideration for all three installations.

Changes in Pole Installation Assessment

In recent years, LADWP has begun to look at the total ownership cost of the pole. In the past, the pole was the only part of the installation cost measured. This was partially because wood has historically been the utility pole material of choice. Wood had a low first cost — the pole itself was inexpensive. But as optimal design and pole management have become more sophisticated, utilities have begun factoring in the equipment requirements, manpower needed, storage and transporting requirements, and maintenance costs for the life of the pole. As a result, alternative-material poles, which are now a more mature sector of the market, have become more attractive than wood poles in some cases.

Higher levels of environmental regulations also have added to the cost of wood poles. The preservatives used to maintain a wood pole's lifespan now require special handling and mandated treatment schedules, depending on the state. California Public Utility Commission (CPUC) now requires 5-year inspections in addition to 10-year intrusive inspections for wood poles. All of these changes, which impact the pole installation and replacement cost, must be calculated into the utility's total cost for a pole installation. But the real concern facing LADWP's engineers was finding a practical alternative to wood poles for space-confined working conditions.

Composite Pole Discussions

Earlier in the year, utility supplier Chuck Bacik from Southwest Power, which is now Hughes Supply (Orlando, Florida), heard about LADWP's special needs. He arranged a meeting to discuss a new product, the RStandard™ modular composite utility pole. There has been much progress in synthetic-type poles and LADWP had previous experience with composite (fiberglass) technology. Other utilities including Southern California Edison were having success with the composite modular pole, particularly in backyard applications. The informational meeting was attended by LADWP engineers and operations personnel, Bacik and a representative from RS Technologies (Calgary, Alberta, Canada), manufacturer of the RStandard composite poles.

Initially, the committee was impressed with the modular design. Modular composite poles, which are lighter than wood poles, are even easier to handle because the pole comes in multiple sections. The subsections can literally be carried by hand into hard-to-reach locations. The low weight and modular design also minimize transportation costs and storage-space requirements.

LADWP thought the composite pole might be a good option for its three problem installations, but the utility was resistant at first to the way the RStandard poles were manufactured. Most composite (fiberglass impregnated with resin) poles are manufactured using the pultrusion process. RStandard poles are manufactured using a proprietary filament-winding process. Filament winding involves winding strands of composite around a rotating mandrel (essentially the mould), creating the various sections of the pole. In the pultrusion process, the composite is pulled through a mold, creating the shape of the pole. The material is then cut at the appropriate length. However, LADWP felt that the proprietary polyurethane resin, Version™, the poles are made with and the modular design made the RStandard poles attractive.

Strength-to-Weight Ratios

The modular composite poles LADWP was considering come in 15-ft and 30-ft segments, 10 mm to 15 mm thick, which are tapered and assembled by putting the sections together. In comparing the composite design to other poles on the market, it has the highest strength-to-weight ratio while meeting or exceeding the strength requirements for the diverse pole classes. A Class-1, 60-ft RStandard pole weighs only 900 lb compared to a 1624-lb steel pole. A wood pole of the same size weighs 2290 lb and a concrete pole weighs 6550 lb.

LADWP also took worker safety into consideration. Moving and installing heavy poles causes many injuries. The lighter composite-based poles reduce the risks associated with heavier poles, and they are made of nonconductive material, another significant safety benefit. Given the tight workspaces, the places with high ground water levels and the alkaline soil, LADWP's Development and Standards Group decided to order the modular composite poles for the three installations.

One of the challenging installations required LADWP crews to remove a wood pole between two buildings and replace it with a taller Class-3, 50-ft pole. The larger pole was needed to upgrade the primary wires on the system where the two primary wires of the 4.8-kV circuit terminated on a 25-kV circuit at the transformer on the pole. The challenge was that there was only approximately 30 inches of space between the two buildings.

Installations

The benefits of using a composite pole became apparent with the transporting of the pole to the work site. Compared to a traditional wood-pole installation, the crew needed no special equipment either to transport the pole or to load and unload it. In fact, the three-piece modular pole sections nested one within the other were tied to the crew's truck rack for delivery to the job site. At the site, there was no need for a boom truck to unload and the sections were literally handled by crew members — one on each end, a section at a time.

At the work site, crews used aerial-lift equipment with a boom winch on the bucket to lift each module separately and sequentially into place. A journeyman in the bucket operated the winch, picking up the base module at its balance point and, following the directions of a journeyman who was on the roof of the building, set it in place. An apprentice and a ground worker also helped position the base section. As the second and third sections were assembled, the apprentice climbed the wood pole being removed to assist in nesting each module into position. He then secured the modules together.

LADWP crews were amazed at how easy the modular poles were to handle in the less-than-ideal work conditions. Crew members also commented that conventional wood-pole replacement, with its heavy equipment requirements, would have been difficult. Transportation logistics were also significantly different. The lighter-weight material and the multisection poles were much easier to handle. Furthermore, the toxic coating that must be used to treat wood poles was eliminated, and down the road, there is zero after-installation maintenance to the composite pole.

Calculating Results

Labor has become the most expensive part of pole-installation cost. The fact that a modular, composite pole can take between one-half and one-third of the time to install compared to other poles is a huge advantage. Installing a traditional Class-3, 50-ft wood pole would have taken up to three days to install. The LADWP calculated that the installed cost of the RStandard pole was approximately 50% less than other poles. Combine this with the expected lifespan of up to 80 years of maintenance-free use, and the Development and Standards Group figures they made a pretty good decision.

Kevin Garrity is group leader of the Development and Standards Group at LADWP. He has been in the utility industry for 23 years, all of which he has been with LADWP. Garrity holds the BSEE, MSEE and MBA degrees. He is a registered professional engineer. kevin.garrity@ladwp.com